The present invention relates generally to a method and apparatus for debarking tree stems and more particularly to a debarking process that utilizes the impact energy from rotating chains or the like to remove bark from the stems as they pass through the debarking station.
Typically tree stems are debarked before undergoing a subsequent conversion process whether it be to convert the tree into lumber products, veneer for plywood manufacture, or chips for pulp manufacture. In addition, when trees are cut from the forest they are typically delimbed to remove the limbs before further processing. Each of these steps preliminary to the conversion process is time consuming and expensive. The limbs and bark can be collected and used as fuel.
The prior art contains a number of different methods for both debarking and delimbing. For example, when delimbing large trees, it is common practice to employ workmen in the woods with chainsaws to simply cut the limbs in the forest before the logs are hauled to the debarking site. With large delimbed logs, debarking methods include high pressure water jets, ring type debarkers where a rotating ring with knives scrapes the bark from the tree, and other well known debarking processes.
Over the years greater quantities of smaller trees are being harvested and converted into useful products. By smaller trees, it is meant trees that are grown and harvested with smaller diameters. Most of the large old growth forests have been logged and many of the forest products companies are now harvesting subsequent growth timber.
For example, in the Midwest and southern growing regions of the United States, many forest products companies are planting, growing and harvesting trees in a cycle that utilizes extensive forest management techniques and harvesting techniques that essentially treat the trees as an agricultural crop. With this type of forest management, typically a significantly larger number of trees are harvested from the same acre of land and the harvested trees will be relatively smaller in diameter. Consequently, in order to maintain production at conversion facilities such as sawmills, plywood plants and chipping facilities, new ways must be found to handle and prepare the trees for conversion. Of course, the ways selected must be cost effecient, safe and suitable for the intended purpose.
Many ways have been disclosed for preparing large quantities of small diameter trees for conversion. For example, it has been suggested that a quantity of trees can be accumulated in bunches and then a chain flail delimbing apparatus utilized to essentially knock the limbs off the trees before they are transported to a debarking site. As with large diameter trees, chain saws may be utilized to remove the limbs, although when handling a large number of relatively small diameter trees, the cost effectiveness of utilizing chain saws goes down. After the small diameter trees are delimbed, then the debarking process must occur before subsequent conversion. Again, if relatively large diameter trees are to be converted into, for example, lumber products the tree stems will typically be debarked utilizing a ring type debarker where a single log is longitudinally passed through the debarking station. While the bark is removed, the production rate is not high in relation to the total costs. When debarking small diameter trees where the debarked trees will be converted into chips, drum type debarkers have been utilized which process a large number of tree stems in a rotating cylinder having means for mechanically removing the bark primarily by a tumbling action. This debarking method also has shortcomings in that the stems must remain in the drum for a long period to remove the bark and as a consequence good wood can be damaged.
What is needed is a method and apparatus that is capable of debarking large quantities of relatively small diameter tree length stems in a substantially continuous manner while at the same time removing the limbs and preferably converting the limbs and removed bark to fuel. Such a system should be capable of accepting a plurality of substantially full length trees with limbs in a side-by-side relationship for transport through a debarking-delimbing station. At the debarking station, substantially all limbs and bark are removed to a level where the debarked and delimbed trees can be fed directly into a chipper. The bark and limbs are fed to a conversion means where they are reduced to suitable size for use as fuel (so called "hog fuel").
Preferably this system should be capable of being, in one form, mobile so that it may be transported to a woods location where the debarking-delimbing and chip conversion can take place. In another form it may be of the stationary type typically located at a conversion facility. An integrated debarking-delimbing system and, if desired, with chipping and fuel preparation apparatus means that several handling steps are eliminated thereby reducing the overall cost of tree preparation for subsequent conversion. If the system is utilized at a woods location, the output of the system can be hauled from the woods in chip and/or fuel form, thereby significantly reducing costs compared to moving whole trees before preparation. Also with such an integrated system, the initial capital investment for meeting the general functional requirement of preparing trees for downstream conversion is significanly less.
As will become very clear to those skilled in the tree handling and conversion art, the present invention will afford significant advantages over state-of-the-art methods and apparatus. In addition, many useful specific applications of the present invention will be apparent in addition to those that are disclosed herein. It should be readily apparent that one of the primary uses of the method and apparatus will be as an economical conversion process for commercial thinnings, which are those trees removed from forests prior to a final commercial harvesting.
Accordingly a primary object of the present invention is the economical debarking of relatively small trees.
Another object of the present invention is the provision of a debarking system integrated with conversion means to reduce handling costs.
Yet a further object of this invention is to provide a high production debarking method meeting the standards for conversion to high quality chips.
Yet another object of this invention is the provision of an efficient high production debarking system that is relatively inexpensive to build and operate.
Still a further object is the provision of a debarking system that can be mobile or stationary depending upon user needs.
Yet a further object of this invention is the provision of a debarking process that also adequately delimbs at high production rates.
Still another object of this invention is the provision of close coupled means to convert the bark, limbs and foliage to usable material and the debarked, delimbed trees to chips.
Yet a further object of this invention is to provide a debarking system that is substantially enclosed to reduce the risk of potential personal injury or property damage.
Still a further object of this invention is the provision of suitable material handling means to keep the flow of material within the system smooth, uniform and consistent, thereby increasing output and reducing the occurrences of downtime due to material backups.
These and many more objects of the present invention will become apparent upon reading the specification to follow in conjunction with the attached drawings.